how can I raise the pressure for chilled water project

[mackistired]

Hi all,
I have a problem on my hand:
I have chilled water project with primary and secondary pumps. The primary loop consist of Three small pumps to ensure that the three chillers we have never starve for water. Each pump is about 15 HP. Now the secondary pumps consist of two on duty and one stand by pump. Each pump is about 50 HP and can push up to 1300GPM. The problem I have is that the water coming from the chillers to the secondary pump is arriving at 65 psi but the pressure at the pump outlet is dropping to 25-30 PSI. This means that my project is getting chilled water at 25-30 PSI which is too low because my highest point of demand is at 35 meters and I need about 60PSI to get it up there. The reason the pressure is high at the inlet of the secondary pumps "I would presume" is because the primary pumps are pushing the water at this PSI. How can I get the pressure to the net work to go up?

[Brian_UK]

Can your secondary pumps produce the required pressure/flow without the primary pumps running?

If not then you need to investigate that problem first.

Does the primary loop feed a low-loss header for the secondary side to take the chilled water from?

Are all of the pumps running with the correct rotation?

Is this the chilled water system that you were referring to when asking about PVC pipework over two and a half years ago? Because we never did hear back from you concerning the answers given.

[goshen]

Can your secondary pumps produce the required pressure/flow without the primary pumps running?

If not then you need to investigate that problem first.

Does the primary loop feed a low-loss header for the secondary side to take the chilled water from?

Are all of the pumps running with the correct rotation?

Is this the chilled water system that you were referring to when asking about PVC pipework over two and a half years ago? Because we never did hear back from you concerning the answers given.

are water strainers clean???

[ref717]

It seems you have insufficient secondary pumps TDH, which is a design issue. You can check the Head of the secondary pumps by looking at its performance curve/graph to see if it would match your system requirements.
Also, what is the chilled water return suction pressure on your primary pumps?,you can try to run 1 more secondary pump in parallel with the 2 pumps to increase both the flowrate and pressure. Check also the volume of water inside your pipe loops, lack of water also makes the pressure down.
Pls. give us your feedback..

[Tesla]

Strange - as you wrote you have 65 psi at the inlet and 25 psi at the outlet of the secondary pumps. Is there a blockage, cavitation and are the pumps running in the correct direction? Are the inlet and outlet pipes sized correctly?